@dain You are right when you mention different systems have different loudness levels at any given dB reading. The Loudness Wars are all about dynamic compression. Soft passages sound almost as loud as the loud ones. It is pretty strange when a single violin sounds as loud as the entire orchestra. People seem to think this sounds better in their cars.
We perceive other issues as "volume" like distortion and sibilance, both want to make us turn it down.
If you do not know about Fletcher-Munson curves read up on it. You can make a system sound louder by modifying it's frequency response to match that of our hearing at any given level, the old Loudness switch.
Next is the volume the recording was mastered at. Recordings mastered at high volumes will sound dull and bass-less at low volumes. Recordings mastered at low levels will sound bright and bassy at loud levels, see Fletcher Munson.
Finally, there is the overall quality of the system. Powerful, low distortion systems ( I include the room as part of the system) with reasonably flat response curves never seem to be playing as loud as they actually are. 95 dB can be very comfortable and satisfying for no longer than an hour or two or you risk damaging your hearing. Volumes above 100 dB should be avoided. But, in order to handle peaks well a system should be able to push out 105 dB without noticeable distress.
@bkeske has it right. Every recording has a "right" volume level again depending on how it was mixed and the type or genre of the music.